290 lines
8.1 KiB
Groff
290 lines
8.1 KiB
Groff
.\" Copyright (c) 1989, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the American National Standards Committee X3, on Information
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.\" Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)strftime.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd June 25, 2012
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.Dt STRFTIME 3
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.Os
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.Sh NAME
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.Nm strftime
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.Nd format date and time
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In time.h
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.Ft size_t
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.Fo strftime
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.Fa "char * restrict buf"
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.Fa "size_t maxsize"
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.Fa "const char * restrict format"
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.Fa "const struct tm * restrict timeptr"
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.Fc
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.Ft size_t
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.Fn strftime_l "char *restrict buf" "size_t maxsize" "const char * restrict format" "const struct tm *restrict timeptr" "locale_t loc"
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.Sh DESCRIPTION
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The
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.Fn strftime
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function formats the information from
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.Fa timeptr
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into the buffer
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.Fa buf
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according to the string pointed to by
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.Fa format .
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The function
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.Fn strftime_l
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does the same as
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.Fn strftime
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but takes an explicit locale rather than using the current locale.
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.Pp
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The
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.Fa format
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string consists of zero or more conversion specifications and
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ordinary characters.
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All ordinary characters are copied directly into the buffer.
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A conversion specification consists of a percent sign
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.Dq Ql %
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and one other character.
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.Pp
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No more than
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.Fa maxsize
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characters will be placed into the array.
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If the total number of resulting characters, including the terminating
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NUL character, is not more than
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.Fa maxsize ,
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.Fn strftime
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returns the number of characters in the array, not counting the
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terminating NUL.
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Otherwise, zero is returned and the buffer contents are indeterminate.
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.Pp
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The conversion specifications are copied to the buffer after expansion
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as follows:-
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.Bl -tag -width "xxxx"
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.It Cm \&%A
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is replaced by national representation of the full weekday name.
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.It Cm %a
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is replaced by national representation of
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the abbreviated weekday name.
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.It Cm \&%B
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is replaced by national representation of the full month name.
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.It Cm %b
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is replaced by national representation of
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the abbreviated month name.
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.It Cm \&%C
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is replaced by (year / 100) as decimal number; single
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digits are preceded by a zero.
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.It Cm %c
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is replaced by national representation of time and date.
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.It Cm \&%D
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is equivalent to
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.Dq Li %m/%d/%y .
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.It Cm %d
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is replaced by the day of the month as a decimal number (01-31).
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.It Cm %E* %O*
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POSIX locale extensions.
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The sequences
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%Ec %EC %Ex %EX %Ey %EY
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%Od %Oe %OH %OI %Om %OM
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%OS %Ou %OU %OV %Ow %OW %Oy
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are supposed to provide alternate
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representations.
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.Pp
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Additionally %OB implemented
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to represent alternative months names
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(used standalone, without day mentioned).
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.It Cm %e
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is replaced by the day of the month as a decimal number (1-31); single
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digits are preceded by a blank.
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.It Cm \&%F
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is equivalent to
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.Dq Li %Y-%m-%d .
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.It Cm \&%G
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is replaced by a year as a decimal number with century.
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This year is the one that contains the greater part of
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the week (Monday as the first day of the week).
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.It Cm %g
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is replaced by the same year as in
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.Dq Li %G ,
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but as a decimal number without century (00-99).
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.It Cm \&%H
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is replaced by the hour (24-hour clock) as a decimal number (00-23).
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.It Cm %h
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the same as
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.Cm %b .
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.It Cm \&%I
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is replaced by the hour (12-hour clock) as a decimal number (01-12).
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.It Cm %j
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is replaced by the day of the year as a decimal number (001-366).
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.It Cm %k
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is replaced by the hour (24-hour clock) as a decimal number (0-23);
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single digits are preceded by a blank.
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.It Cm %l
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is replaced by the hour (12-hour clock) as a decimal number (1-12);
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single digits are preceded by a blank.
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.It Cm \&%M
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is replaced by the minute as a decimal number (00-59).
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.It Cm %m
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is replaced by the month as a decimal number (01-12).
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.It Cm %n
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is replaced by a newline.
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.It Cm %O*
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the same as
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.Cm %E* .
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.It Cm %p
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is replaced by national representation of either
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"ante meridiem" (a.m.)
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or
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"post meridiem" (p.m.)
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as appropriate.
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.It Cm \&%R
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is equivalent to
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.Dq Li %H:%M .
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.It Cm %r
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is equivalent to
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.Dq Li %I:%M:%S %p .
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.It Cm \&%S
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is replaced by the second as a decimal number (00-60).
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.It Cm %s
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is replaced by the number of seconds since the Epoch, UTC (see
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.Xr mktime 3 ) .
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.It Cm \&%T
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is equivalent to
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.Dq Li %H:%M:%S .
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.It Cm %t
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is replaced by a tab.
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.It Cm \&%U
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is replaced by the week number of the year (Sunday as the first day of
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the week) as a decimal number (00-53).
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.It Cm %u
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is replaced by the weekday (Monday as the first day of the week)
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as a decimal number (1-7).
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.It Cm \&%V
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is replaced by the week number of the year (Monday as the first day of
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the week) as a decimal number (01-53).
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If the week containing January
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1 has four or more days in the new year, then it is week 1; otherwise
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it is the last week of the previous year, and the next week is week 1.
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.It Cm %v
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is equivalent to
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.Dq Li %e-%b-%Y .
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.It Cm \&%W
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is replaced by the week number of the year (Monday as the first day of
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the week) as a decimal number (00-53).
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.It Cm %w
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is replaced by the weekday (Sunday as the first day of the week)
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as a decimal number (0-6).
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.It Cm \&%X
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is replaced by national representation of the time.
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.It Cm %x
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is replaced by national representation of the date.
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.It Cm \&%Y
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is replaced by the year with century as a decimal number.
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.It Cm %y
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is replaced by the year without century as a decimal number (00-99).
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.It Cm \&%Z
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is replaced by the time zone name.
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.It Cm %z
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is replaced by the time zone offset from UTC; a leading plus sign stands for
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east of UTC, a minus sign for west of UTC, hours and minutes follow
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with two digits each and no delimiter between them (common form for
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RFC 822 date headers).
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.It Cm %+
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is replaced by national representation of the date and time
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(the format is similar to that produced by
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.Xr date 1 ) .
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.It Cm %-*
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GNU libc extension.
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Do not do any padding when performing numerical outputs.
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.It Cm %_*
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GNU libc extension.
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Explicitly specify space for padding.
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.It Cm %0*
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GNU libc extension.
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Explicitly specify zero for padding.
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.It Cm %%
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is replaced by
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.Ql % .
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.El
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.Sh SEE ALSO
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.Xr date 1 ,
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.Xr printf 1 ,
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.Xr ctime 3 ,
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.Xr printf 3 ,
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.Xr strptime 3 ,
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.Xr wcsftime 3
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.Sh STANDARDS
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The
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.Fn strftime
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function
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conforms to
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.St -isoC
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with a lot of extensions including
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.Ql \&%C ,
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.Ql \&%D ,
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.Ql %E* ,
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.Ql %e ,
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.Ql %G ,
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.Ql %g ,
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.Ql %h ,
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.Ql %k ,
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.Ql %l ,
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.Ql %n ,
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.Ql %O* ,
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.Ql \&%R ,
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.Ql %r ,
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.Ql %s ,
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.Ql \&%T ,
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.Ql %t ,
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.Ql %u ,
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.Ql \&%V ,
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.Ql %z ,
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.Ql %+ .
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.Pp
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The peculiar week number and year in the replacements of
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.Ql %G ,
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.Ql %g
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and
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.Ql \&%V
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are defined in ISO 8601: 1988.
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The
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.Fn strftime_l
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function conforms to
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.St -p1003.1-2008 .
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.Sh BUGS
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There is no conversion specification for the phase of the moon.
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.Pp
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The
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.Fn strftime
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function does not correctly handle multibyte characters in the
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.Fa format
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argument.
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